1. Field of the Invention
The present invention relates to a floating type magnetic head having a slider that initially contacts a recording medium and then floats above the recording medium when the operation of a recording medium is started and more particularly, to a floating type magnetic head that is capable of reducing static friction force between a slider and the recording medium such that the force required to start the operation of the recording medium is also reduced.
2. Description of the Prior Art
FIG. 8 is a perspective view showing a floating type magnetic head for use in, for example, a hard disk apparatus in such a manner that the surface of the floating type magnetic head confronting the disk faces upwards.
The floating type magnetic head H, as shown in FIG. 8, has the top surface that is caused to face the recording surface of a hard disk which is a magnetic recording medium.
The floating type magnetic head H has a portion located upstream (portion a) with respect to direction x, in which the disk is moved, the portion being called a leading portion, and a portion located downstream (portion b) that is called a trailing portion. The slider 1 is made of a ceramic material or the like, and has an end surface 2 in the trailing portion b, to which a thin-film device 3 is attached. The thin-film device 3 comprises: a magnetic detection portion (an MR device portion) that uses magnetoresistive effect to reproduce a magnetic signal recorded on the disk; and a recording portion (an inductive device portion) having a pattern-formed coil or the like.
The slider 1 has, on its surface that faces the disk, rail portions 4 on the two sides of an air groove 7 thereof. The surfaces of the rail portions 4 are formed into air bearing surfaces (ABS) 5, that are in contact with the disk when the disk is stationary (that is, not rotated). An inclined surface 6 is formed at a leading end of each the air bearing surfaces 5.
The slider 1 of the magnetic head H is supported by a flexure secured to the leading end of a load beam, the slider 1 being urged against the disk with weak force of about 4 g (gram) by the elastic force of the load beam formed by a leaf spring. The magnetic head H is employed in a so-called CSS (Contact-Start-Stop) type hard disk apparatus in such a manner that the air bearing surfaces 5 of the slider 1 are brought into contact with the recording surface of the disk due to the forgoing urging force when the operation (rotation) of the disk is stopped. When the operation of the disk has been started, an air flow is, in the direction (in the direction X), in which the disk is moved, introduced between the slider 1 and the surface of the disk so that the slider 1 is caused to float above the surface of the disk by a short distance. The amount of floating of the slider 1 from the disk is determined due to the depth of the air groove 7 and to the surface areas of the air bearing surfaces 5.
When the slider 1 is being caused to float, the slider 1 has an attitude such that the leading portion (a) is raised higher than the trailing portion (b). In the foregoing attitude of floating, magnetic signals recorded on the disk are read by the magnetic detection portion of the thin-film device 3 or magnetic signals are recorded on the disk by the magnetic recording portion.
A motor for operating the disk, that is provided for the CSS-type hard disk apparatus, must have a starting torque which is capable of causing the disk and the slider 1 to reliably start the sliding operation. If the torque required to start the sliding operation between the disk and the slider is enlarged, the hard disk apparatus must be provided with a large-size motor. Thus, there arise problems in that the size of the apparatus cannot be reduced and that the electric power consumption is enlarged excessively.
The torque required to start the operation of the disk depends upon the static frictional force between the air bearing surfaces 5 of the slider 1 and the surface of the disk. To reduce the starting torque required for the disk, the foregoing static frictional force must be reduced.
The static frictional force has been reduced by a method in which each of the air bearing surfaces 5 is formed into a curved shape (a crown shape) having a large curvature radius or a method in which fine concavities and convexities are formed on the surfaces of the air bearing surfaces 5. By forming each of the air bearing surfaces 5 into the crown shape or by forming the fine concavities and convexities on the surfaces of the same, the area of actual contact between the air bearing surfaces 5 and the disk can be reduced.
However, forming of each of the air bearing surfaces 5 into the crown shape having a predetermined curvature radius requires a very difficult polishing operation, whereby the manufacturing process becomes too complicated. What is worse, the crown shape having the predetermined curvature radius cannot stably be formed, and thus mass production encounters a critical problem. If the concavities and convexities are formed on the surfaces of the air bearing surfaces 5, the air bearing surfaces 5 scratch the surface of the disk at the time of starting the operation of the disk, whereby the surface of the disk can easily be damaged.
Accordingly, in recent years, it might be considered feasible to employ a method of reducing the area of actual contact with a disk D by forming, on the air bearing surfaces 5, projections 5a, each having a somewhat large area, by etching the air bearing surfaces 5, as shown in FIG. 9. However, the etching process has too complicated steps and, thus, the cost required to machine the slider 1 cannot be reduced. In addition, the etching process for making the height .delta. of the stepped portion of the projection 5a to be uniform encounters a difficulty and there arises a problem in that the height .delta. varies among manufactured products.
Although the foregoing crown shape, fine concavities and convexities and the projections formed by the etching process are able to reduce the area of contact with the disk, the static frictional force between the disk and the slider 1 is not determined by only the area of contact but it is considerably affected by the lubricant on the surface of the disk and by a water screen adhered to the surface of the disk.
Lubricant having a thickness of several nm (nanometers) is applied to the surface of the hard disk. If the relative humidity in the environment in which the hard disk is used is about 50%, a water drop having a thickness of several nm adheres to the surface of the disk. In a state where the operation of the disk is stopped, the lubricant and water screen are allowed to intervene between the disk and the slider 1, thus causing the slider 1 to be adsorbed onto the disk. As a result, there arises a problem in that the static frictional force for sliding the slider 1 and the disk with respect to each other is enlarged excessively.
Although the method, in which the air bearing surfaces 5 are formed into the crown shapes, is able to reduce the area of contact, intervention of a liquid film formed by the lubricant and the water screen cannot be prevented. Also in the case where the fine concavities and convexities are formed on the surfaces of the air bearing surfaces 5, the foregoing liquid film intervenes among the fine concavities and the disk. In either case, the static frictional force cannot satisfactorily be reduced.
The maximum thickness of the liquid film formed by the lubricant and the water screen is about 10 nm. Therefore, in the structure as shown in FIG. 9, in which the projection 5a having a somewhat large area is formed on each of the air bearing surfaces 5 by the etching process, liquid film A is, due to the surface tension, formed among the air bearing surfaces 5 and the surface of the disk if the height .delta. of the stepped portion of the projection 5a is lower than 10 nm. The adsorbing force of the liquid film A undesirably enlarges the static frictional force. With the method, in which the projection 5a is formed by the etching process, the height .delta. of the stepped portion cannot easily be adjusted. If the value of the height .delta. is enlarged, a long time takes place to complete the etching process and thus a manufacturing cost cannot be reduced.
The conventional floating type magnetic head is usually formed into a bulk type having a structure such that a core, around which a coil is wound, is attached to the end of the trailing portion. In recent years, a structure, in which a thin-film device 3 is, as shown in FIG. 8, disposed on to the end surface 2 of the trailing portion, has been widely used. The structure comprising the thin-film device 3 as described above must have a protective film formed in a portion 8 in which the thin-film device 3 is exposed to the air bearing surface 5. In particular, a structure of a type, that the thin-film device 3 is provided with the magnetic detection portion (the MR device portion) that uses the magnetoresistive effect, encounters leakage of the electric current flowing in the device portion because a detection electric current is supplied to the device portion if the protective film, that is capable of electrically insulating the electric current, is not provided. Thus, there arises a problem in that the magnetic detection cannot be performed.
Since the size of the slider 1 of the foregoing type is too small to form the protective film in only the exposed portion 8, the protective film is usually formed on the entire surfaces of the air bearing surfaces 5 as well as the exposed portion 8. If the fine concavities and convexities are, as described above, formed on the air bearing surfaces 5 in the foregoing case so as to reduce the area of contact, the protective film is introduced into the fine concavities. Thus, the effect of reducing the static frictional force by forming the fine concavities and convexities cannot be attained satisfactorily.
In the case where the projection 5a having a somewhat large area is formed as shown in FIG. 9, the protective film is formed after the projection 5a has been formed by etching. If the protective film having a predetermined thickness is formed on the surfaces of the projection 5a and the air bearing surfaces 5, making of the height .delta. of the stepped portion to be a value larger than a predetermined value encounters an aggravated difficulty.